【作者】 梁利平；

【导师】 吴汉宁；

【作者基本信息】 西北大学 ， 油气田地质与开发， 2014， 博士

【摘要】 在我国油气能源供应日趋紧张和国外页岩气开发取得突破的环境下,我国对页岩气藏的开发逐年重视,并视其为促进能源结构调整的重要部分。过去两年,我国的页岩气开发取得了突破性进展,以涪陵示范区为标志的川渝页岩气开发区实现了单井15×104m3/d,累产7300×104m3的成果,使我们对页岩气的开发充满了期待和希望。然而,开发页岩气藏需要具备一定的进行大规模水力压裂的条件,这就要求页岩储层具有一定密度和连通性的天然裂缝,而对于复杂天然裂缝网络的描述非常困难；另一方面,不同于常规低渗透油气藏,页岩气的渗流不仅存在达西流动,还存在气体吸附解吸过程和扩散流动,这些渗流机理的共同作用使得页岩气渗流规律非常复杂。解决以上两个问题是实现对页岩气藏进行产能预测这一目标的必要途径。本文首先对四川须家河组页岩露头进行了物理性质实验测试,包括矿物分析、岩石密度测试、水平地应力测试、三轴应力测试、抗张抗剪强度测试等。结果发现,以水平地应力差、杨氏模量和泊松比、岩石脆性为判别指标时,四川须家河组页岩均符合形成裂缝网络的条件；从抗张抗剪强度测试结果可知,页岩水平方向具有优先开裂的条件；以硬度测试为基础,利用无声致裂剂致裂并统计岩心压裂的裂缝条数、崩落的碎块和裂缝面密度的方法,提出了判断页岩气藏形成网状裂缝的标准。然后,以黑油模型为基础模型,以气体总量相等为原则,采用溶解气代替吸附气的方法,通过Fracman生成的离散裂缝网络模拟复杂的天然裂缝,完善了单一介质黑油模型模拟页岩气的产能预测模型,对比传统的双孔单渗模型模拟结果发现,二者均能较好地进行页岩气产能预测。第三,对影响页岩气单井产量的诸多参数进行了模拟,如基质渗透率、人工裂缝参数、天然裂缝参数、吸附气量等。结果发现,页岩气单井产量与基质渗透率、人工裂缝长度、人工裂缝条数、天然裂缝导流能力、天然裂缝连通性和吸附气量均呈正比,与天然裂缝间距成反比；通过正交试验方法对各因素进行了主次排序,对产能的影响程度从强到弱依次为基质渗透率、人工裂缝长度、天然裂缝间距和吸附气量,并通过层次分析法和BP试验法对这一排序进行了验证；通过大量的数值模拟计算进行了图版绘制,并以BP人工神经网络的方法对各因素对改造体积的影响关系进行训练,从而用以快速确定任意条件下的改造体积形状和大小。最后,对实际页岩区块A进行了模拟计算,对比了水平井和直井开发实际页岩区块的产能情况,并对采用水平井开发时的裂缝参数进行了优化,为该区块的开发提供理论指导。更多还原

【Abstract】 The development of shale gas reservoirs in our country is paid more and more attention and seen as an important part to modify the energy structure, since the supply of energy is inadequate in our country and the development of the shale gas increases quickly in other countries. In the past two years, the development of the shale gas in our country is so fast that the daily gas production in falling representative area achieves15×104m3/d and the cumulative gas production reaches7300×104m3, this bring us expectation and hope. However, the conditions of conducting large volume hydraulic fracturing operation should be needed to develop shale gas reservoirs. One of these conditions is complex fracture network and methods to express it in computer; another is to understand thoroughly the permeate mechanism in shales. Since the permeate method not only include Darcy flow in large pores and channels but also desorption process and diffusion process in small pores and channels, all of these mechanisms make a unimaginable complex permeate condition. Therefore, how to solve the above two questions is a necessary way to achieve shale gas production prediction.First, this paper conducts lots of tests on outcrops in Sichuan Xujiahe shale play, including mineralogical analysis, rock density test, horizontal terrestrial stress test, triaxial stress test and tensile strength and shearing strength test, etc. The results show that the shale in Sichuan Xujiahe shale play can generate a fracture network after large volume stimulation on the basis of results of horizontal terrestrial stress, Young’s modulus and Poisson ratio, rock brittleness. The shale is easily fractured in the horizontal direction on the basis of results of tensile strength and shearing strength. Through summarizing the fracture number, fragments and fracture surface density after fracturing using silent agent, a new criterion to judge the possibility to create fracture network is developed. Second, on the basis of black oil model and mass conservation law, we use the dissolved gas to replace the adsorbed gas and using Fracman to generate the discrete fracture network, so the single medium model to simulate shale gas production is modified. Compared with the double hole single permeability model, both of them yield reasonable result, which means the modified single medium model is appropriate to simulate shale gas production. Third, simulate the effect of matrix permeability, artificial fracture parameters, natural fracture parameters and adsorbed gas volume on shale gas production. The results show that the production is in proportional to matrix permeability, artificial fracture length, artificial fracture number, natural fracture conductivity, natural fracture connection and adsorbed gas volume, and is inversely proportional to natural fracture interval. The order to influence the production is obtained through orthogonal test method and proved by analytic hierarchy process and Plackett-Burman (BP) test method. With large amounts of simulations, the calculated plate for quick parameter determination is created. Through practicing the effects of different factors on the shape and size of the stimulated reservoir volume using BP artificial neutral network method, the quick parameter determination for any condition can be achieved. Finally, simulate the real shale gas reservoir A. Through comparison of horizontal well production and vertical well production, horizontal well is more appropriate to develop the shale gas reservoir. The fracture parameters are also optimized to provide theoretical guidance to the development of this reservoir.更多还原